Fact Sheet: At War With Weeds

Sophie demonstrates how to tackle annual and perennial weeds efficiently and effectively

Presenter: Sophie Thomson, 02/11/2013

SERIES 24 Episode 33

Sophie shows how to deal with persistent garden weeds

"Weeds, like any garden plant, are either annuals or perennials," says Sophie. "By learning to recognise which group your weeds fall into, you can learn to deal with them effectively - and that's what I'm going to show you."

These annual weeds complete their lifecycle within a year and rely on setting seed to establish the next generation, so if you can stop them feeding, eventually you can get rid of the weeds.

"Mallow is not only unsightly, it presents my plants with root competition and provides winter habitat for one of my worst pests - the harlequin bugs. Last year, they sucked the life out of my tomatoes, so by getting rid of these weeds, I'm actually going to solve two problems," says Sophie.

Members of the mallow group grow up to about a metre high and have a thick, deep root system. Hand-pulling them once they get to a reasonable size is hard work, but to stop them setting seed, cut them very low with a whipper snipper or mower when they flower. You can even cut back small patches off at ground level with secateurs! This method also works well with other annuals like flickweed, cleavers and the grasses. The critical thing with annual weeds is to make sure you get rid of them before they have a chance to flower and set seed.

Perennial weeds are more of a challenge because they keep growing year after year, flowering and seeding as they go. Sophie's dealing with couch grass (Cynodon dactylon), kikuyu grass (Pennisetum clandestinum), field bindweed (Convolvulus arvensis), dock (Rumex sp.) and the perennial grasses, phalaris (Phalaris sp.).

Many perennial weeds have an underground storage organ - a bulb, rhizome, stolon, or even just a long, fleshy taproot - and if you don't get it all out, the plant will come back.

"Dock is a great example," says Sophie. "It has a really long, fleshy taproot. The only time to try and dig this up is when the ground's nice and moist. It has a really serious root system, so when you're digging it up, be as diligent as you can."

Some of the toughest perennial weeds to deal with are the running grasses like couch and kikuyu. Sophie likes to deal with them by smothering them to death. The process is called sheet mulching.

First, wet the ground thoroughly, apply a layer of organic fertiliser - which aids the breakdown of the weeds - then apply soaked newspaper in thick layers. Make sure the layers overlap and when done, top with a thick layer of organic mulch. Leave it alone for at least three months and you're left with fertile, weed-free soil.

Whilst Sophie prefers not to use chemical herbicides, she occasionally relies on an organic option. It's based on pine oil and works by burning the weeds' foliage.

"By learning to identify the weeds in your garden, you'll have access to a wealth of information about their lifecycles which is the key to dealing with them successfully, leaving you more time to do the gardening tasks you enjoy," Sophie ends.

Information contained in this fact sheet is a summary of material included in the program. If further information is required, please contact your local nursery or garden centre.

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